Quote Originally Posted by engloshy View Post
Thank you so much guys for your cooperation.

Sir/Madam Emsr2d2,

I used gentlemen because I am talking (contact) with a group of people and I don't know their gender in general.
As I said, there is no need for any salutation of any kind. If you want to include one, you can say "Hello everyone" - that is as formal as you need to be! By the same token, you do not need to put "Sir/Madam + username" - just put the username.

For your info, referring to a gender-unknown group of people as "Gentlemen" doesn't work because it specifically excludes the women. If you wanted to include everyone, you would say "Dear Ladies and Gentlemen".